The present invention relates to rotary joints for conveying feedwater to rotating machines, such as combustors.
In the operation of a rotary device, such as a combustor, it is necessary to supply feedwater to piping mounted for rotation with a rotating member, such as a barrel. The feedwater is supplied from, and returned to, a stationary water supply system. Therefore, the water supply system must be connected to the piping via a rotary joint supporting a shaft tube assembly which typically rotates about an axis coaxial with that of the rotary device.
Known rotary joints include a stationary housing enclosing a rotatable shaft tube assembly, with packings, usually of fibrous material, being employed to provide a seal between the shaft tube and the stationary housing. In the known structures, such packings must be provided at each end of the housing.
While such structures initially provide a satisfactory seal, it has been found that they develop leaks after a comparatively short period of time, apparently due to the fact that they lose their resiliency as the result of cyclic thermal expansion and contraction of the shaft tube assembly during repeated shutdowns and startups of the equipment.